Re: OOM killer changes

[Ralf-Peter Rohbeck <Ralf-Peter.Rohbeck@quantum.com>]

On 17.08.2016 23:57, Vlastimil Babka wrote:
>>>> Hmm. I added linux-next git, fetched it etc but apparently I didn't check
>>>> out the right branch. Do you want next-20160817?
>>> Yes this one should be OK. It contains Vlastimil's patches.
>>>
>>> Thanks!
>> This has been working so far. I built a kernel successfully, with dd
>> writing to two drives. There were a number of messages in the trace pipe
>> but compaction/migration always succeeded it seems.
>> I'll run the big torture test overnight.
> Good news, thanks. Did you also apply Joonsoo's suggested removal of
> suitable_migration_target() check, or is this just the linux-next
> version with added trace_printk()/pr_info()?
>
> Vlastimil
Yes, that change was in my test with linux-next-20160817. Here's the diff:

diff --git a/mm/compaction.c b/mm/compaction.c
index f94ae67..60a9ca2 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1083,8 +1083,10 @@ static void isolate_freepages(struct 
compact_control *cc)
                         continue;

                 /* Check the block is suitable for migration */
+/*
                 if (!suitable_migration_target(page))
                         continue;
+*/

                 /* If isolation recently failed, do not retry */
                 if (!isolation_suitable(cc, page))
diff --git a/mm/migrate.c b/mm/migrate.c
index f7ee04a..b1176a4 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -827,8 +827,10 @@ static int fallback_migrate_page(struct 
address_space *mapping,
          * We must have no buffers or drop them.
          */
         if (page_has_private(page) &&
-           !try_to_release_page(page, GFP_KERNEL))
+           !try_to_release_page(page, GFP_KERNEL)) {
+               trace_printk("try_to_release_page failed for 
a_ops:%pS\n", page->mapping->a_ops);
                 return -EAGAIN;
+       }

         return migrate_page(mapping, newpage, page, mode);
  }
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5637733..b443652 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3202,8 +3202,12 @@ should_compact_retry(struct alloc_context *ac, 
int order, int alloc_flags,
          * But do not retry if the given zonelist is not suitable for
          * compaction.
          */
-       if (compaction_withdrawn(compact_result))
-               return compaction_zonelist_suitable(ac, order, alloc_flags);
+       if (compaction_withdrawn(compact_result)) {
+               int ret = compaction_zonelist_suitable(ac, order, 
alloc_flags);
+               if (!ret)
+                       pr_info("XXX: no zone suitable for compaction\n");
+               return ret;
+       }

         /*
          * !costly requests are much more important than __GFP_REPEAT
@@ -3227,6 +3231,7 @@ check_priority:
                 (*compact_priority)--;
                 return true;
         }
+       pr_info("XXX: compaction retries fail after %d\n", 
compaction_retries);
         return false;
  }
  #else

It ran the whole night with continuous torture tests and writing to two 
drives. No OOM.
Logs are at 
https://filebin.net/l2kp3iit8dj0fq6q/OOM_4.8.0-next-20160817.tar.bz2.

Thanks for fixing this!
Ralf-Peter

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